Electric switch



y 1950 w. G. BOURNE 2,516,670

ELECTRIC swncn Filed Feb. 23, 1949 2 Sheets-Sheet 1 y 1950 w. G. BOURNE 2,516,670

ELECTRIC SWITCH Filed Feb. 23, 1949 2 Sheets-Sheet 2 mazml If 6,.250ur126 Patented July 25, 1950 ELECTRIC SWITCH William George Bourne, Acton, London, England, assignor to Rotax Limited, London, England Application February 23, 1949, Serial No. 77,866 In Great Britain February 26, 1948 1 Claim. 1

This invention has for its object to provide an improved electric switch of the push-button type adapted to be actuated automatically under the action of an overload.

The invention comprises the combination of a fixed contact piece, a pivoted contact arm carrying or serving as the movable contact piece, an over-centre spring device for imparting quick closing and opening movements to the said arm, a spring loaded toggle linkage for actuating the said spring device, a catch for controlling the toggle linkage, a push button for actuating the said linkage in one direction, and a second push button and a thermally operable means for r leasing the catch and thereby enabling the toggle linkage to be actuated in the opposite direction by the associated spring.

In the accompanying drawings, Figure 1 is a sectional front elevation of a switch embodying the invention, and illustrating the fixed and movable contact parts, with the toggle mechanism associated with the movable contact part. Figure 2 is a sectional front elevation of the switch, illustrating the catch mechanism, and Figure 3 is a sectional plan of the switch.

Referring to the drawings, there is mounted on an insulating base a, a fixed contact piece I). Also on the base are mounted or formed appropriate supports for carrying the switch mechanism. On one of the supports is pivoted at one end of an arm d which at its other end has formed on or secured to it the movable contact piece e. Coaxially with this arm is pivoted a bell crank lever forming part of an over-centre spring device. To one end of this lever is pivotally attached one end of a stem 9, the other end of which is slidably supported in a swivel piece It on the outer end of the arm d. A spring 2 surrounding the stem and supported by the said swivel piece and the opposite end of the stem, serves to impart the desired quick closing and opening movements to the arm. The other end of the bell crank lever has pivotally connected to it one end of one (i) of a pair of links forming a toggle linkage, the opposite end of the other (k) of these links being pivotally attached to another arm n pivoted at m and loaded by a spring 0. The arm n is carried by another of the supports on the base, and is controlled by a catch as hereinafter described. The junction of the two toggle links is carried by a slide p which is loaded by a spring q and is movable in the direction for closing the switch by a push button 1 projecting through a cover piece s which encloses the switch mechanism.

The arm n has formed on or secured to it a part if (Figures 2 and 3) which can engage one end of a three-armed or T-shaped lever u serving as the catch. Another arm of this lever is operable by a second spring loaded push button .11 through a spring arm w, and the third arm is operable by a bi-metal strip 1a through an adjustable push piece 11 secured to the strip, the latter being deformable by the heating effect of the current flowing when the switch is closed. The bimetal strip may be of any convenient form adapted for connection between a terminal piece and the fixed contact 17. Thus (in plan) it may be of U or like form having the part 1 at its closed end, and its other ends connected to a terminal piece and the contact b respectively.

The arrangement is such that closing of the switch is efiected by pressing inwards the push button r. This, by its action on the slide p, moves the toggle linkage is from one side to the other of a line through the opposite ends of the links. In so doing this linkage operates the overcentre spring device 1, g, i and causes the latter to move the associated contact arm d to the closed position. In this action the arm n is held stationary by the interaction of the parts it, u. The switch can be opened by the push button 1) or by the bi-metal strip at. In either case the lever 14 is thereby moved away from the asso ciated arm part if and consequent movement of the associated arm n by its spring 0 enables the spring q acting on the slide p to move the toggle linkage in the direction for opening the switch, the said arm part t being then re-engaged by the catch lever it. But when the catch is released by the action of the bi-metal strip, the catch cannot re-engage the arm until the strip re-assumes its normal condition.

By this invention I am able to provide a push button switch of the type specified in a compact and convenient form.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

An electric switch or" the type specified, comprising in combination a fixed contact piece, a pivoted contact arm for co-operating with said contact piece, a spring loaded toggle linkage, an over-centre spring device connecting said toggle linkage to said contact arm so that said spring device serves to impart quick opening and closing movements to said contact arm under the action of said toggle linkage, a catch for con trolling said toggle linkage, a push button for moving said toggle linkage in one direction, and a second push button and a thermally operable member for releasing said catch and thereby enabling said toggle linkage to be returned by its spring loading to its initial position after being actuated by the first mentioned push button.

WILLIAM GEORGE BOUR-NE.

REFERENCES CITED Name Date Bottinger et al. July 21, 1942 Number 

